1. Field of the Invention
The present invention relates to a receiving apparatus and a transceiver which receive superposition signals obtained by superposing a plurality of signals by a plurality of antennas and separate individual signals from the received signals.
2. Related Background Art
In a transmission apparatus of a wireless communication system, a technique in which different transmission symbols are transmitted from transmission antennas on the same resource (for example, on the same time and the same frequency) by using a plurality of transmission antennas and receiving antennas, and individual signals are separated from the superposition signals obtained by superposing a plurality of transmission symbols, in order to separate and estimate the individual signals. This is a technique for increasing capacity of transmission rate at larger amount than the wireless communication system using a single antenna. The technique is called MIMO (Multiple Input Multiple Output).
For example, G. J. Foshini has proposed in “Layered Space-time architecture for wireless communication in a fading environment when using multi-element antennas”, Bell Labs Technical Journal, pp. 41–59, Autumn, 1998, a communication system which has plurality of antennas both at the transmitter and receiver. This is called BLAST (Bell Labs Layered Space-Time). The BLAST converts transmission symbols of serial data into parallel data, and then transmits different symbols with the same frequency from the transmission antennas at the same time. The receiving apparatus deals with the transmission symbols from the transmission antennas as interference, and eliminates interference and recover the individual symbols by using the antennas of more than the number of the antennas of the transmission apparatus. Because of this, in the BLAST, if characteristics of channel impulse response between the antennas, it is possible to obtain the capacity of M times (M is the number of the transmission antennas) of capacity of transmission rate by the conventional single antenna.
Incidentally, according to the conventional techniques (BLAST), weight vectors which are orthogonal to vectors constituted by the channel impulse response from the transmission antennas could be generated to eliminate the interference. The number of the required receiving antennas has to be the same as or more than the number of the transmission antennas. Because of this, in cellular system and so on, when the BLAST is used for down link from the wireless base station to the wireless terminal, there is a problem in which the number of the antennas of the wireless terminals increases and downsizing of the wireless terminal becomes difficult.